This is very damaging indeed as it suggests - despite insisting yesterday "there is no leadership issue", the Business Secretary may, after all, have been involved in plotting to unseat Nick Clegg.

Vince Cable, who's in China, has yet to comment on the claims.

For years, Lord Oakeshott has made no secret of the fact he believes Nick Clegg is hindering not helping the party's prospects. But his suggestion, in his resignation statement, that the party is "heading for disaster" under Mr Clegg's leadership is likely to lead to more turmoil in the party's ranks over the coming days.

"A busted flush" is how one senior source described Lord Oakeshott to me, but that may turn out to be wishful thinking.